This document summarizes a presentation on modeling water allocation to Murray Valley wetlands across the Murray-Darling Basin. Some key findings from the modeling include: - Wetland connectivity to river channels is important for aquatic vegetation and species presence. Regulation has reduced connectivity for many wetlands. - There is greater resilience and more wetlands achieving maximum diversity with higher discharge levels above nominal levels, both before and after regulation. - Concordance between wetland indicators was high before regulation but low after, suggesting regulation has fragmented the river into discrete management units. - Weir pool manipulation and artificial flooding can help sustain aquatic communities and ecosystems, as shown with flooding trials at Chowilla floodplain.

1. Water Research Centre
Water Wednesday
Sustaining the River Murray with less water

2. Water Allocation to Murray Valley wetlands: a
basin wide modelling approach
George Ganf,
University of Adelaide
Rod Oliver, CSIRO
Sean White, University of Adelaide
Justin Brookes, Kane Aldridge, Dominic Skinner,
Mike Young
Supported by Land & Water Australia (sadly, no
more)

3. Wetland Plants

4. 7000+ wetlands

5. Fro this
m To this

6. Summary of major findings
• Connectivity
• Linking aquatic vegetation with hydrology
Pre- v. post-regulation
•Resilience
•Fragmentation
The ecological unit
•Management for ecological benefit
•The reach
•Weir pool manipulation (Chowilla initiative)

7. Connectivity – a surrogate index of water
regime
• 0.91- 1.0 = continuous connection to main
channel (permanently wet)
• 0.41- 0.5 = 41 - 50% of time connected to main
channel (seasonal inundation)
• 0.0- 0.09 = Never or rarely connected

8. CONNECTIVITY

9. P - v. p s g tio > 10 0w tla s
re o t-re ula n 0 e nd
lo t c nne tio w m in c nne
s o c n ith a ha l

10. Gaussian distribution curves describing probability of
presence for 4 species across a gradient in wetland-river
connectivity.
1.0
Eleocharis acuta
Potamogeton crispus
Phyla canescens
0.8
Phragmites australis
Probability of presence
0.6
0.4
0.2
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Connectivity

11. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

12. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

13. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

14. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

15. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
Pre-
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

16. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
Pre-
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

17. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
Pre-
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
30000
Post 1500
20000 1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

18. Pre- v. post regulation – influence of discharge above nominal
(1989-2000) on # wetlands that achieve maximum diversity
60000 3000
Pre-
50000 2500
Cumulative area of wetlands (ha)
Cumulative number of wetlands
40000 2000
RESILIENCE
30000
20000
Post 1500
1000
Nominal
10000 Discharge 500
0 0
-10000 -8000 -6000 -4000 -2000 0 2000
-1
Discharge (GL yr )

19. -10000 -8000 -6000 -4000 -2000 0 2000 -6000 -5000
Discharge (GL yr-1)
60000 3000 60000
B E
Cumulative number of wetlands
Cumulative wetland area (ha)
Cumulative wetland area (ha)
50000 2500 50000
Natural
40000 2000 40000
Family 30000 1500 30000
20000
Current 1000 20000
10000 500 10000
0 0 0
-20000 -15000 -10000 -5000 0 -4000 -300
Discharge (GL yr-1) Nominal Discharge
60000 3000 60000
C F
Cumulative number of wetlands
Cumulative wetland area (ha)
Cumulative wetland area (ha)
50000 2500 50000
Natural
Functional 40000 2000 40000
30000 1500 30000
20000 1000 20000
10000 Current 500 10000
0 0 0
-20000 -15000 -10000 -5000 0 -1000
Discharge (GL yr-1) Nominal Discharge

20. Pre-regulation - Strong concordance – suggested
that response of one indicator is associated with
other indicators across all reaches
Post-regulation – Not significant
Suggests river regulation and extraction has
segmented the river into discrete units whose
wetland indices respond discordantly to changes
in discharge and therefore must be managed
individually

21. Pre-regulation - Strong concordance – suggested
that response of one indicator is associated with
other indicators across all reaches
FRAGMENTATION
Post-regulation – Not significant
Suggests river regulation and extraction has
segmented the river into discrete units whose
wetland indices respond discordantly to changes
in discharge and therefore must be managed
individually

22. Artificial watering (pumping)
V.
Weir pool manipulation
sustaining the resilience of aquatic
communities and at the ecosystem level

24. Inund tio a ao theC w
a n re f ho illa
flo d la a lo flo s(10 0 ML/d y
o p in t w w ,0 0 a
flo toSA), w a w ut a
w ith nd itho n
enviro e l re ula r o e tingo
nm nta g to p ra n
lo e C w C e (SA MDB NRM
w r ho illa re k
Bo rd 2 0 ).
a 08